Laser Etching Process of TSV and Reliability Analysis of TSV-based IC structure by Finite Element Simulation

TSV is a kind of subversive technology, which breaks through the bottleneck of planar integration technology by filling conductive materials such as copper, tungsten, and polysilicon in the through hole to achieve vertical three-dimensional integration. In TSV technology, some physical properties should be concerned, such as thermal expansion coefficient difference between the filled metal and the silicon matrix, which can lead to stress concentration reliability problem and even cause the failure of the entire TSV-based 3D packaging structure after accumulation. In this paper, a picosecond laser with a wavelength of 355nm was used to drill holes in silicon wafers. Based on the configuration parameters and the morphology of holes, a TSV with specific depth to width ratio was studied. The numerical simulation software COMSOL Multiphysics was used to simulate the stress distribution of the copper filled TSV with different percentages. The simulation results showed that the lower the metal filled percentage, the smaller the maximum thermal stress of the TSV column; compared to metal materials, TSV filled with polysilicon has the lowest thermal stress. Also, it can be found that the stress of polysilicon-filled TSV is higher than that of polysilicon-unfilled TSV under the same copper-filled percentage. In full filling state, the more the polysilicon content, the less the stress inside TSV. Furthermore, seen from the temperature cycle simulation of other filling materials (polysilicon, nickel alloy, tin lead alloy), polysilicon, nickel alloy, tin lead alloy is also suitable for metallization materials analyzed from the perspective of thermal stress distribution.